Adafruit METRO M0 Express - designed for CircuitPython

Arduino-form-factor board built around the ATSAMD21G18 ARM Cortex-M0+, designed for CircuitPython. Compatible with the Arduino IDE as a step up from the ATmega328-based Metro 328.

Micro USB
Primary board power input over Micro USB; source states about 5 V at 500 mA, with temporary fuse shutoff above about 1000 mA.
Type · powerVoltage · 5V USB input
DC jack
5.5 mm / 2.1 mm centre-positive DC input; source states provide about 6 V to 12 V to power the Metro.
Type · powerVoltage · 6V-12V input
3V
Output from the 3.3 V regulator; source states it can supply 500 mA peak.
Type · powerVoltage · 3.3V output
5V
5 V rail from the regulator when DC jack is used, or from USB; source states about 500 mA peak from USB and 800 mA peak from DC.
Type · powerVoltage · 5V output
GND
Common ground for all power and logic.
Type · groundVoltage · 0V

Start wiring

USB · 3.3 V

Confirm the data interface matches your host board.

Module pins: Micro USB, DC jack, 3V, 5V, Vin, IORef, GND, #0 / RX. Schematik maps them to your board in the app.

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Specialists: Teensy for high-clock audio and USB, Adafruit SAMD boards running CircuitPython or the Arduino IDE, proper STM32 eval kits, and the micro:bit classroom ecosystem. Schematik builds target ESP32, Arduino Uno, and Pico; come here when you have a specific reason to.

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Position

Type

Function

Voltage

Micro USB

power

Primary board power input over Micro USB; source states about 5 V at 500 mA, with temporary fuse shutoff above about 1000 mA.

5V USB input

DC jack

power

5.5 mm / 2.1 mm centre-positive DC input; source states provide about 6 V to 12 V to power the Metro.

6V-12V input

power

Output from the 3.3 V regulator; source states it can supply 500 mA peak.

3.3V output

power

5 V rail from the regulator when DC jack is used, or from USB; source states about 500 mA peak from USB and 800 mA peak from DC.

5V output

GND

ground

Common ground for all power and logic.

Vin

power

Higher of the DC jack or USB voltage; source gives 9 V example for DC input and 5 V when only USB is connected.

USB/DC input rail

#0 / RX

signal

GPIO 0 and Serial1 hardware UART receive input.

3.3V logic

#1 / TX

signal

GPIO 1 and Serial1 hardware UART transmit output.

3.3V logic

#2-#12

signal

General-purpose GPIO pins; source states most pins can do PWM output and all except D4 can be interrupt inputs.

3.3V logic

#13 / L

signal

GPIO 13, connected to the red LED marked L next to the USB jack.

3.3V logic

SDA

signal

I2C Wire data pin; source notes no default pull-up, so an external 2.2 kΩ to 10 kΩ pull-up may be needed.

3.3V logic

SCL

signal

I2C Wire clock pin; source notes no default pull-up, so an external 2.2 kΩ to 10 kΩ pull-up may be needed.

3.3V logic

analog

Analogue input A0 and true analogue output via DAC; source states output can be set from 0 V to 3.3 V.

0V-3.3V analogue

A1-A5

analog

Analogue input pins that can also be used as digital I/O.

3.3V logic / analogue input

SCK

signal

Hardware SPI clock pin, also connected to the 2x3 SPI header.

3.3V logic

MOSI

signal

Hardware SPI MOSI pin, also connected to the 2x3 SPI header.

3.3V logic

MISO

signal

Hardware SPI MISO pin, also connected to the 2x3 SPI header.

3.3V logic

RST

control

Reset pin; tie to ground to manually reset the ATSAMD21 and launch the bootloader manually.

3.3V logic

ARef

analog

External analogue reference input; source states it cannot go higher than 3.3 V.

<=3.3V reference

IORef

power

Digital reference voltage pin; source states it is the same as the 3.3 V logic voltage and cannot be changed.

3.3V reference

SWD header

programming

2x5 0.05 inch SWD debug interface for trace debugging, external programming, or non-bootloader development.

3.3V logic

Pinout

Start wiring

Arduino

ESP32

Add-ons

Pi Pico